Skip to content

Answer the following. (Class 10 Science 2025, Q27)

questionbuddy.in/q/cbse-10-science-2025-31-1-1-q27

ScienceCBSE Class 10 · Board exam 2025, set 31/1/1 · 3 marks · Short answer

CBSE Class 10 Science 2025: question 27

Set in the CBSE Class 10 board exam of 2025, paper 31/1/1, section C, question 27, for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q27 · 3 marks · Short answerMetals and Non-metals

Answer the following.

  1. (a)

    "Displacement reactions also play a key role in extracting metals in the middle of the reactivity series." Justify this statement with two examples.

    0 marks
  2. (b)

    Why can metals high up in the reactivity series not be obtained by reduction of their oxides by carbon?

    0 marks

Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 31/1/1.

Hints

Open one hint at a time and try again before the next.

Hint 1

Which highly reactive metal is used to reduce metal oxides in the thermit process?

Hint 2

Compare how strongly carbon and sodium or magnesium hold on to oxygen.

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

  1. (a) Oxides of moderately reactive metals such as Mn and Fe can be reduced by a more reactive metal like aluminium, which displaces them. These reactions give out so much heat that the metal is obtained in the molten state.

  2. (a) Example 1:

    1 mark

  3. (a) Example 2 (thermit reaction, used to join railway tracks):

    1 mark

  4. (b) Metals high in the reactivity series, such as Na, Ca, Mg and Al, have a greater affinity for oxygen than carbon has. Carbon cannot remove oxygen from their oxides, so these metals are extracted by electrolytic reduction instead.

    1 mark

Answer: (a) 3MnO₂ + 4Al → 3Mn + 2Al₂O₃ + heat; Fe₂O₃ + 2Al → 2Fe + Al₂O₃ + heat; (b) these metals have more affinity for oxygen than carbon

Where the marks are

  • First correct displacement reaction, e.g. MnO₂ with Al (1 mark)
  • Second correct displacement reaction, e.g. Fe₂O₃ with Al (thermit) (1 mark)
  • These metals have more affinity for oxygen than carbon (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from Metals and Non-metals, one at a time, marked against the answer key and marking points.Back to the full paper2025 board paper, set 31/1/1: every question, by section.

The question is transcribed from the official paper; figures are described in words. The solution, hints and chapter tag are ours. Spotted an error? Write tosupport@questionbuddy.in.